The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Powertrain systems include torque generator(s), e.g., an internal combustion engine and/or torque machine(s) powered by non-fossil fuel. The torque machine(s) powered by non-fossil fuel include e.g., stored electric energy, stored hydraulic energy, and stored pneumatic energy. The torque generator(s) transfer torque via a transmission device to a driveline for traction to propel a vehicle.
Meshed driveline components, e.g., transmission splines and interleafed gearing teeth on planetary gear sets, have clearances that are a result of manufacturing tolerances and component design specifications. Such clearances facilitate assembly, accommodate build variation and thermal expansion of the components, allow for lubrication, and permit deflection of teeth under load conditions. Gear lash, i.e., play or slack in relative rotational positions of the meshed driveline components, results from the clearances between the meshed components.
A torque reversal is a torque transition event wherein torque transfer across meshed driveline components transitions from transferring torque in a first rotational direction to transferring torque in a second, opposite rotational direction. During a torque reversal, existing gear lash causes a period during the transition wherein zero torque is transferred between the meshed driveline components in either rotational direction. When gear lash is subsequently closed, impacts between the meshed driveline components produce clunks (i.e., audible noises) and jerks (e.g., physical lurches), either of which may be objectionable to a vehicle operator and may cause undue stress on the meshed driveline components.
Torque reversals may be the result of an operator shifting a transmission from a Park position to either a Drive position or a Reverse position, or shifting between the Drive and Reverse positions. Torque reversals may occur during ongoing operation due to a throttle tip-in when an operator commands a vehicle to accelerate while the vehicle is coasting, or a throttle tip-out. In a throttle tip-in, the driveline is initially exerting torque on the powertrain system by way of engine braking or regenerative braking, and the command to accelerate results in a torque reversal when the engine or motor/generator begins exerting torque on the driveline. In a throttle tip-out, there is an opposite torque reversal.